1946] 
Luminescence in Fire-flies 
13 
JUVENILE AND IMAGINAL LUMINESCENCE IN 
FIRE-FLIES (LAMPYRIDiE) 
By Charles T. Brues 
Biological Laboratories, Harvard University 
In spite of the extensive literature relating to luminous lampy- 
rids very slight attention has been paid to those forms in which 
the light-producing organs of the adult beetle are greatly re- 
duced in size and brilliance. 
On June 15th the writer collected at Petersham, in central 
Massachusetts, a number of pupae which were provided with 
luminous organs near the tip of the abdomen. In general ap- 
pearance and in the size, form and position of these organs 
they resembled the pupae of one of our common native fireflies, 
Photuris pennsylvanica , which appears abundantly every year 
at this locality later in the month of June. The pupae were at 
the bottom of a pile of old boards that had been thrown into 
an open field some years ago and were rapidly undergoing final 
decay and dissolution. Altogether, 54 pupae were secured and 
put by in the laboratory to follow the expected development of 
the imaginal light organs. 
Some of these pupae began to transform into beetles during 
the following night and their emergence continued for a period 
of a week. To our surprise, however, the eclosed adults were 
not Photuris, but another common lampyrid, Lucidota atra 
Fab. represented by individuals of both sexes. 
It has been generally observed that the small larval pair of 
photogenic organs persist in the pupae and may pass over into 
the adult, e.g., in Photinus consanguineus where the male re- 
tains the larval organs in addition to his much larger and sepa- 
rate imaginal one which is developed as a purely adult structure. 
Lucidota belongs to a small group of related genera in which 
the imaginal photogenic organs are feeble and consist entirely 
of the remains of the precursory juvenile structures. To this 
group belongs also Pyropyga, a species of which (P. fenestralis 
Mels.) has been observed by Hess 1 to possess larval light organs 
which continue to function throughout the pupal period. He 
1 Biol. Bull., vol. 38, pp. 39-76 (1920). 
